I started playing the mod yesterday and I cant figure out how to get water. Some guides on Youtube made it sound like you begin with a refillable canteen, but all I have are painkillers, a bandage and a flashlight. Can you fill up the empty whiskey bottles that are lying around everywhere?

You did use to start with a canteen, but not anymore.
You can either find a canteen, which you can refill at ponds creeks or whatever or just pick up the sodacans that lie around literally in every house, even on some zeds.

You will have to get a Canteen as mentioned above, walk into the water (sea water is no longer usable source of filling your Canteen btw), theres plenty of ponds , and a few Well's around to refill it.

But do remember, when going down to a pond to refill it, DO NOT SWIM!, you will lose your backback, just walk out up to your knee's at most if your not able to fill it from the side, but don't go deeper as you will lose your backback, and you can't get it back once you lost it (aka you have to find a new one:P) been there done that lol, same goes for the ocean, don't swimxD

Funny how you can't drink straight from the pond or the well. Rocket must be a germ freak, or thinks the girls will leave their lipstick on the spout. (Office awareness)Turns out the drinking bottles the girls bring to fill at the dispenser were leaving the lipstick marks, not one of the girls drinking straight from it.

Also another tip. When you are in the gear window, sometimes upon closing it you will drop ammo for weapons that you don't have or are not using. This can be a pain in the ♥♥♥♥ if you need that ammo later.

Don't try putting firearms in your backpack. So far more often than not for me they have only disappeared, and wind up being dropped below the floor, along with the ammo I mentioned above.

Make sure you are not standing in the door jambs when closing doors. Which means make sure you are not in another door jamb thinking you're closing the door in front of you, but actually just shut the door you're standing in, and you die as the force of the door crushes you.

Don't crawl/prone across door jambs unless you like broken legs. If your legs are already broken you'll probably die. I also died once by going prone next to a bush and tree. This doesn't happen a lot, but seems to happen at the wrong times.

These are good tips to keep you from wanting to scream after surviving for several days only to die or loose stuff through glitches.